“The Golden Hour.” It was a term coined a long time ago – in 1975, when wars were fought much differently, and Dr. R. Adams Cowley, the founder of Baltimore’s Shock Trauma Center, asserted that the first hour after injury would largely determine a critically injured person’s chances for survival. The golden hour has never been a perfect metric, but for military medical professionals, it emphasized the urgency of getting wounded warfighters out of the theater and into trauma care. In 2009, U.S. Secretary of Defense Robert Gates issued a golden hour mandate: Prehospital helicopter transport of critically injured casualties must be done in 60 minutes or less. According to a 2015 report in JAMA Surgery, the secretary’s mandate saved a total of 359 lives.

“We have increasing data that 90 percent of the KIA [killed in action] are lost in the first 10 minutes after wounding.” The overwhelming majority of those deaths, Smith said, are due to blood loss, or hemorrhage.

For U.S. service members, the wars in Afghanistan and Iraq dramatically narrowed the window of time available for the critically wounded to survive, as improvised explosive devices (IEDs) became their adversaries’ weapons of choice, and blast injuries far outnumbered gunshot wounds among coalition warfighters. The Washington Post, working from Pentagon casualty notices, has estimated that, through 2014, more than 2,500 service members were killed by IEDs in Afghanistan and Iraq. According to a 2013 article in USA Today, “How the IED Changed the U.S. Military,” the Pentagon has estimated that somewhere between more than half to two-thirds of Americans killed or wounded in combat in Iraq and Afghanistan were victims of “IEDs planted in the ground, in vehicles or buildings, or worn as suicide vests, or loaded into suicide vehicles.”

According to Dale Smith, Ph.D., professor of military medicine and history at the Uniformed Services University of the Health Sciences (USU), the hour is no longer golden: “We have increasing data that 90 percent of the KIA [killed in action] are lost in the first 10 minutes after wounding.” The overwhelming majority of those deaths, Smith said, are due to blood loss, or hemorrhage.

It would be reasonable to expect much lower survival rates among warfighters who’ve had limbs blown off or suffered multiple injuries – polytrauma – from IEDs. But in December 2013, a trio of military medical experts – Capt. (Dr.) Eric Elster, USU’s chair of surgery; Army Gen. (Dr.) Eric Schoomaker, Ph.D., the recently retired U.S. Army surgeon general; and Dr. Charles Rice, then USU’s president – posted a blog entry on the healthaffairs.org website explaining that actually, the opposite had happened. “At the beginning of operations Enduring Freedom (OEF) and Iraqi Freedom (OIF), the combat injury case-fatality rate was approximately 18 percent,” they wrote. “Over the subsequent decade, it steadily decreased to 5 percent despite an overall increase in injury severity.”

This decrease was achieved by improvements throughout the entire spectrum of trauma care, including:

• preventive measures such as armoring and training in the doctrine of Tactical Combat Casualty Care (TCCC);
• better point-of-injury treatment with improved tourniquets and anticoagulants that helped slow rates of hemorrhaging;
• improved “damage control resuscitation” procedures, including a new blood transfusion protocol;
• the use of “damage control surgery” to focus on stabilizing a patient for transport to definitive care; and
• at the level of definitive care – a hospital, for example – the promotion of long-term healing with negative-pressure (vacuum) dressings and silver dressings.

Despite the significant improvements in combat trauma survival rates over the past decade-and-a-half, both military and civilian leaders in trauma care acknowledge room for further improvement. Last year, citing advances in both civilian and military trauma care, the National Academies of Science, Engineering, and Medicine published a report, “A National Trauma Care System: Integrating Military and Civilian Trauma Systems to Achieve Zero Preventable Deaths After Injury.” The report presented “a vision for a national trauma care system driven by the clear and bold aim of zero preventable deaths after injury and minimal trauma-related disability to benefit those the nation sends into harm’s way in combat as well as every American.”

 

Survivable Wounds: The “Target of Opportunity”

How will the military know when it’s achieved zero preventable deaths? According to Terry Rauch, Ph.D., acting deputy assistant secretary of defense for health readiness policy and oversight, one of the most influential recent studies of battlefield medicine was conducted by Col. (Dr.) Brian Eastridge, a retired Army surgeon and former director of the Joint Theater Trauma System (now the Joint Trauma System). Eastridge examined the circumstances of 4,596 American combat deaths between 2001 and 2011, Rauch said, and, “almost 75 percent of them were due to explosions … and it’s most important for us to realize from this analysis that the overwhelming majority of all deaths by traumatic injury, nearly 90 percent, happened before the patient reached a medical treatment facility. That focuses our attention on where we need to improve care: It’s at the point of injury and the time taken to transport them to the MTF [medical treatment facility].”

“About 25 percent were deemed potentially survivable by Eastridge’s analysis,” Rauch said. “So that is a target of opportunity for us. More than 90 percent of those deaths were associated with hemorrhage. So if you look at where we can make the most difference in focusing our technologies and research investments, it’s in stopping the bleeding at the point of injury.”

Eastridge’s study of these pre-hospital deaths, published in the Journal of Trauma and Acute Care Surgery in 2012, determined that a little over 75 percent were due to catastrophic, “nonsurvivable” injuries; those patients either died instantly or would have died no matter when they’d arrived at an MTF. “About 25 percent were deemed potentially survivable by Eastridge’s analysis,” Rauch said. “So that is a target of opportunity for us. More than 90 percent of those deaths were associated with hemorrhage. So if you look at where we can make the most difference in focusing our technologies and research investments, it’s in stopping the bleeding at the point of injury.”

The period Eastridge studied was a time of considerable progress in that area, Rauch said. The fielding of tourniquets, which had become widespread after 2007, and the implementation of TCCC undoubtedly saved many lives. Combat deaths due to hemorrhage from limb trauma – bleeding out of an arm or leg – have become increasingly rare. The vast majority of hemorrhage deaths, said Rauch, are caused by injuries to non-compressible anatomical sites, such as the torso or trunk. “More than two-thirds of those with ‘potentially survivable’ wounds were lost due to truncal hemorrhage,” he said. “And then about 20 percent were lost because of junctional hemorrhage – your armpit or your groin.”

IED blasts often cause pelvic fractures and high leg injuries, which result in massive blood loss if not immediately treated, but in recent years, Army and Navy medical researchers have field tested junctional tourniquets that, while not quite as simple to use as extremity tourniquets, can be deployed in about a minute and stop bleeding with inflatable bladders that compress arteries against adjacent bone. The SAM® Junctional Tourniquet, one such device, was cleared by the Food and Drug Administration (FDA) in 2013 for inguinal (groin) use, and was later cleared for axillary (armpit) use and pelvic binding.

While bleeding from the trunk poses a greater risk of death – its major blood vessels, including the aorta, cannot be compressed from the outside, as a tourniquet does – recent innovations have solved this problem by supplying compression from the inside. About a decade ago, Drs. Todd Rasmussen and Jonathan Eliason, Air Force surgeons in Iraq, began looking at ways to adapt a method used in hospitals to stop aortic bleeding during surgery: the resuscitative endovascular balloon occlusion of the aorta (REBOA) catheter. Inserted via the femoral artery, it could be deposited at or above the site of an aortic wound and inflated to block blood flow – but the surgical version was cumbersome and required X-ray guidance. Rasmussen and Eliason refined it into a smaller, stripped-down version, the ER-REBOA™ Catheter, that could be used by forward surgical teams in small field hospitals to stop bleeding from the aorta, the primary conduit from the heart to most of the body.

The XSTAT, developed by the Oregon-based RevMedx, Inc., is basically a large-bore syringe filled with tiny sponges impregnated with coagulant. Once injected into a wound, the sponges expand to fill the wound cavity and apply pressure, providing a physical barrier to blood flow for up to 4 hours.

Deployment of a REBOA catheter is a potentially dangerous procedure – aortic blood flow can only be cut off for about 30-40 minutes before causing irreversible damage to the tissues of the legs and internal organs – and requires training. But it offers precious time to get a wounded patient to an MTF, where a surgeon can pack the wound and stop bleeding before deflating the catheter.

Rasmussen and Eliason fielded their first version of the ER-REBOA Catheter in 2009, and the idea was picked up and developed by the startup Prytime Medical. Cleared for distribution by the FDA in 2015, the catheter has saved lives in both military and civilian settings.

Since 2015, an innovative hemostatic dressing, the XSTAT®, has been successfully used by far-forward military medical personnel to stop bleeding from wounds in normally non-compressible junctional sites. The XSTAT, developed by the Oregon-based RevMedx, Inc., is basically a large-bore syringe filled with tiny sponges impregnated with coagulant. Once injected into a wound, the sponges expand to fill the wound cavity and apply pressure, providing a physical barrier to blood flow for up to 4 hours. The FDA cleared the XSTAT for use in both military and civilian trauma cases in May 2016.

The XSTAT’s application, however, is mostly limited to junctional wounds; it’s not indicated for wounds to the trunk – the abdomen and thorax. Wounds here, as Rauch pointed out, account for the majority of preventable combat deaths due to blood loss, and until recently, there was no good choice for preventing blood loss from truncal wounds.

In early 2017, the Army Medical Materiel Agency took its first steps toward a clinical trial to evaluate the safety and effectiveness of what Rauch calls an “intracavity noncompressible hemorrhage control agent”: an expandable foam, remarkably similar to the agent used to seal and fill household gaps and cracks, that can be injected into a wound to provide a “bridge to surgery.” The culmination of a public/private project launched in 2010 and led by the Defense Advanced Research Projects Agency, the “rescue foam,” as Rauch calls it, “is a self-expanding biocompatible material that you can administer at the point of injury to stop massive blood loss in casualties suffering from abdominal trauma. You inject the material, and it fills and conforms to the abdominal cavity and controls the bleeding.” The foam can be left inside the patient for up the 3 hours, buying valuable time for a patient to be transported to a surgical facility for definitive care.

 

The Microenvironment: The Surgical Critical Care Initiative

Efforts to improve combat wound care and healing, as Elster pointed out, have been implemented at every point along the continuum of care, and a recent initiative involving multiple partners in the military medical community – including USU, Walter Reed National Military Medical Center, Duke University, Emory University, and DecisionQ, a predictive analytics company – is aimed at optimizing recovery from traumatic wounds in definitive care settings.

“We’re building these tools not to replace but to enhance the decision-making of clinicians.”

When a person suffers a traumatic wound, Elster explained, the timing of its final closure is a critical decision. “We call it delayed primary closure – a skin graft may be placed over the wound, or some type of complex flap reconstruction is performed.” The timing of that final closure is determined based on when the surgeon estimates the risk of infection is lowest. “That decision is made correctly about 85 percent of the time,” Elster said, but that means surgeons get it wrong 15 percent of the time. “And there’s a price to that: more time in the hospital, more risk of complications, a longer period of time before you rehabilitate and get where you need to go – and a dollar cost, as well. In fact, when you get that single decision wrong, it creates about $60,000 in hospital-associated costs.”

The Surgical Critical Care Initiative (SC2i) is a precision medicine initiative, designed to create decision tools for surgeons that combine a patient’s clinical information with data about inflammatory biomarkers – both local, from the wound exudate, and systemic – and produce a target window for optimal wound closure. “Systemic inflammation and the local response can change the microbial flora,” said Elster, “so you have an infection, or an impairment of the ability of those proteases involved in remodeling to effectively begin the process of wound healing.” The idea, Elster said, is to focus wound care around a patient’s individual biology, rather than to blindly follow traditional protocols. “We’re building these tools not to replace but to enhance the decision-making of clinicians.” About 1,600 patients around the country have been enrolled in evaluations of SC2i’s decision tools.

Many U.S. service members remain deployed overseas, and while the number of casualties has decreased significantly in recent years, Elster said the military medical community isn’t taking anything for granted: Efforts are underway in the military medical community to maintain and even accelerate the gains that have been made in lowering the rate of preventable combat deaths. The Joint Trauma System continues to refine and codify clinical guidance for the continuum of patient care – working in collaboration with civilian counterparts to achieve the vision of a national trauma care system that approaches zero preventable deaths – while implementing training and education programs to maintain currency and competency among expeditionary surgical teams.

“We’ve gotten better, even as the enemy has gotten more resourceful in their ability to cause injury,” said Elster. “But we need to maintain and build proficiency – to not only keep that combat fatality rate at 6 percent, but to drive it down even further.”